In general, a metal interconnection is used to electrically interconnect devices in a semiconductor device. Aluminum (Al), aluminum alloy, and tungsten (W) are often used as the material for a metal interconnection.
However, since semiconductor devices are highly integrated, it is difficult to use such metals because of their low melting points and high specific resistances. Copper (Cu), gold (Au), silver (Ag), cobalt (Co), chromium (Cr), and nickel (Ni) all have excellent conductivity and can be used as the material for a metal interconnection. Particularly, copper and copper alloy, which have low specific resistivity, excellent reliability for electron migration (EM) and stress migration (SM), and low production cost, have been widely used.
Metal interconnections using copper are often formed using a damascene process. The damascene process forms a trench in an insulating layer through a photo process and an etching process and then fills a conductive material in the trench, such as W, Al, or Cu. Next, the majority of the conductive material is removed, leaving a required interconnection using an etch-back or chemical mechanical polishing (CMP) method, thereby forming an interconnection having the shape corresponding to the trench.
However, copper is not suitable for a dry etching process and does not easily adhere to SiO2. Copper also has low thermo-dynamical stability and low resistance against corrosion. Furthermore, copper may serve as a deep level dopant that is diffused into silicon to produce acceptor and donor states in a band gap, thereby causing a leakage current or malfunction of a device.
Thus, there exists a need in the art for an effective diffusion barrier layer that can be used with copper.